The invention relates to a valve device, in particular a window and lens cleaning device in motor vehicles.
There is a device which essentially comprises a plastic nozzle housing with a duct, two nozzles inserted at its end and also a connecting piece which is inserted into the duct on the other side and is fastened therein in a sealed manner, for feeding a cleaning liquid to the nozzles. At its end which faces the nozzles, the tubular connecting piece is provided with a nonreturn valve. This prevents the cleaning liquid from flowing back if the delivery pressure is reduced, for example by the relevant pump being switched off.
In detail, the known nonreturn valve is of similar construction to the inner tube valves known from older bicycle inner tubes. On its nozzle-side end, the tubular connecting piece is closed but has at least one hole in its circumferential surface. This hole is covered by a thin and elastic flexible tube which is pulled over the outside of the connecting piece. If the pressure in the interior of the connecting piece rises, the flexible tube is raised slightly due to the liquid emerging from the hole. This liquid then flows between the outer circumferential surface of the connecting piece and the inner wall of the flexible tube and emerges toward the nozzles.
Despite the relatively simple external construction, this arrangement has certain disadvantages with regard to flow through the nonreturn valve. The twisted and constricted overflow cross section increases the throttle resistance. On leaving the flexible tube, the liquid is as it were abruptly relieved of tension and atomized, with the result that an undesirable development of noise has to be attended to. In addition, at least at the beginning of each spraying process, if the region between the nonreturn valve and the nozzles is still empty or is only partially filled, for example because of evaporation, an air-water mixture is fed to the nozzles, the desired cleaning action thereby being reduced initially due to deficient spray pressure.